1. Field of the Invention
The present invention relates to a head slider and a disc drive unit employing the same head slider, and more particularly to a head slider which can reduce a sticking force or a stiction produced between the head slider and a recording medium, when they are brought into contact with each other when a disk drive unit starts up or stops, and to a disk drive unit employing the same head slider.
2. Description of the Related Art
In recent years, as magnetic disk drive units have been made smaller in size while their capacities have been increased, various innovative technologies have been introduced in order to provide faster and more reliable disk drive units. Similar innovations in technology have been demanded for disk media which carry out writing and reading of data.
However, as the magnetic disk drives have been made smaller in size and their capacities have been increased, flying heights of heads have decreased, and as the flying heights have decreased, the surfaces of the disk media have been made smoother. The head is mounted on a distal end portion of a head slider and is allowed to fly above a disk medium by the slider with an extremely small gap relative to the disk medium while a magnetic disk drive unit is in operation for writing and reading data into and from the disk medium.
On the other hand, when the power supply of the magnetic disk drive unit is switched off, the rotational speed of the disk medium decreases, whereby the head slider and the disk medium come into contact with each other and, eventually, the head slider comes to rest on the disk medium which then stops rotating. In the event that head slider stops on the disk medium having a smooth surface, a case where the head slider and the disk medium come to stick to each other may occur. In order to prevent this, a plurality of short legs, which are referred to as pads and have small contact areas, are provided on a conventional head slider on a side thereof facing the disk medium in such a manner as to protrude therefrom, whereby the head slider is constructed to rest on the disk medium on the legs.
On the contrary, when the power supply is switched on for the magnetic disk drive unit, a spindle motor for rotating the disk medium repeatedly rotates forward and backward to determine its rotating direction. In the worst case, there is a probability that the spindle motor rotates backward, and when this actually happens, the posture of the head at rest is such that the head is no longer supported by the legs as described previously but is instead supported at an end portion of the flying surface of the head slider.
In the event that the head slider is supported relative to the disk medium at the end portion of the flying surface thereof, the contact area between the head slider and the disk medium increases, and the sticking force or stiction of the head slider to the disk medium also increases, this deforming the head, whereby in the worst case there occurs a probability that a head crash may be caused. Countermeasures for this have been desired.
Additionally, in recent years, due to provision of high-density disk drive units, in an improved head slider in which the difference in level between an air bearing of the head slider and a head portion is reduced, the distance between the head portion and a disk medium has been gradually decreased. Due to this, in an improved head slider, when there occurs a reverse rotation of the disk medium, which modifies the posture of the head slider at rest, there is caused a problem that the head portion first comes into contact with the disk medium before an end face of the air bearing of the head slider comes into contact with the disk medium or both the end face of the air bearing of the head slider and the head portion come into contact with the disk medium. Then, in the event that both the end face of the air bearing of the head slider and the head portion come into contact with the disk medium when the disk medium rotates backwards, there is caused a problem that the contact area between the head slider and the disk medium increases, whereby the stiction therebetween increases.